Seismic Design of Concrete Basin Walls

[houselaw]

I am working on a project that involves the design of water-filled, soil buried rectangular concrete basins in a Seismic Design Category D area and the design is based on the ACI 318-19 code. The walls are retaining soil and liquid loads (static and seismic), they are fixed at the bottom and pinned at the top, and I am designing them to yield at the bottom. I would appreciate your thoughts on the following:

1) Should the walls be designed as one-way slabs (with all the ACI 318-19 relevant requirements for slabs, including for instance minimum slab reinforcement, rebar spacing etc.)?
2) Which part of ACI 318-19, Chapter 18 covers the seismic design of the basin walls?
3) Should the wall vertical and horizontal longitudinal reinforcement be designed assuming that the stress in the flexural tensile reinforcement is 1.25fy or fy?
4) Which part of ACI 318-19, Chapter 18 covers the calculation of seismic development lengths for standard hooks and straight bars for the basin walls?
5) Should a 1.25fy factor be applied to the seismic development length equations for the walls?

 

[HTURKAK]

My comments ;


- ACI318-19 Clause 1.4.9 This Code does not apply to the design and construction of tanks and reservoirs.

- Commentary to Clause 1.4.9 R1.4.9 Requirements and recommendations for the design and construction of tanks and reservoirs are given in ACI 350, ACI 334.1R, and ACI 372R.

- ACI 350.3 tanks
• Walls perpendicular to the direction of the ground otion being investigated shall be analyzed as slabs
subjected to the horizontal pressures computed in Section 5.3.


My suggestion would be , pls look to the relevant codes and then ask specific questions if any..









I cannot give you the formula for success, but I can give you the formula for failure..It is: Try to please everybody.

 

[houselaw]

@HTURKAK, thanks for your feedback and for sharing the references. I am using both ACI 350 and ACI 350.3 but somehow I missed that statement in ACI 350.3 for the walls to be analyzed as slabs out-of-plane. I guess I was looking too hard in ACI 318 and ACI 350 for answers to this (sigh...). Thanks again for pointing this out. As for the other references, I haven't used ACI 334.1R and ACI 372R before but I will try to get access to them to take a look through my company.

Any thoughts on my questions on the seismic development lengths and the stress to be considered in the flexural tensile reinforcement for the seismic design of the walls (=slabs)? To the best of my understanding, ACI 350 is copying the seismic sections of ACI 318 verbatim and ACI 318 does not seem to be clear on the seismic design of slabs yielding in flexure (at least to me with limited experience in seismic design so far).

 

[HTURKAK]

Dear houselaw (Structural)(OP);

You do not provide a lot of information here .. With the limited info . (buried tank , is not clear for me rectangular or circular, depth ,size , fully buried or not ...) I will try to respond your questions ..

1) Should the walls be designed as one-way slabs (with all the ACI 318-19 relevant requirements for slabs, including for instance minimum slab reinforcement, rebar spacing etc.)?
A= Decide Acc. to aspect ratio one-way or two -way slabs design ..

2) Which part of ACI 318-19, Chapter 18 covers the seismic design of the basin walls?

A= ACI 318-19 does not apply to the design and construction of tanks and reservoirs.


3) Should the wall vertical and horizontal longitudinal reinforcement be designed assuming that the stress in the flexural tensile reinforcement is 1.25fy or fy?
A= The reinforcement should be designed assuming that the stress in the flexural tensile reinforcement is fy...

4) Which part of ACI 318-19, Chapter 18 covers the calculation of seismic development lengths for standard hooks and straight bars for the basin walls?
A= ACI 318-19 does not apply to the design and construction of tanks and reservoirs .But you may look to the OMF beam development length requirements

5) Should a 1.25fy factor be applied to the seismic development length equations for the walls?

A= NO..


- When you look ACI 350.3 Table 4.1.1(b)—Response modification factor R, It is clear that the R factors are not applicable for full plastic hinge development ..

- When you look ASCE 7-16 , 15.7 TANKS AND VESSELS Clause 15.7.3 Strength and Ductility

- f. For concrete liquid-containing structures, system ductility and energy dissipation under unfactored loads shall not be
allowed to be achieved by inelastic deformations to such a degree as to jeopardize the serviceability of the structure.
Stiffness degradation and energy dissipation shall be allowed to be obtained either through limited microcracking,
or by means of lateral force resistance mechanisms that dissipate energy without damaging the structure.

I will suggest you to provide more info . to get better responds ..( Tank dimensions , seismicity , how did you calculate Ac, Ai , Base shear , ..)

My opinion ..






I cannot give you the formula for success, but I can give you the formula for failure..It is: Try to please everybody.